Optical fibers may have been widely used for the propagation of optical signals, especially to provide high speed communication links. Optical links using fiber optics may have various advantages over electrical links, for example, comparatively large bandwidths, comparatively high noise immunity, comparatively reduced power dissipation, and comparatively minimal crosstalk. Optical signals carried by optical fibers may be processed by a wide variety of optical and/or optoelectronic devices, including integrated circuits.
Photonic integration, or the coupling of the end of an optical fiber to the edge of an integrated circuit, may be playing an increasingly important role in optical systems. As used herein, the phrase photonic integration may mean optical coupling between an optical waveguide and an optical fiber. Photonic integration may bring about various benefits, such as a relatively smaller footprint, a higher port density, a reduced power consumption, and/or a reduced cost, which may render photonic integration a promising technology for building the next generation of integrated optical devices, such as wavelength division multiplexing (WDM) transponders, transceivers, and other types of devices.
Coupling light in and out of the silicon waveguide chip may be a challenging area due to the differences in waveguide structure from conventional waveguides. Grating coupling is a historic solution to silicon chip coupling, wherein direct butt coupling places the end of an optical fiber in contact with the waveguide, for example, at an about vertical orientation with respect to a horizontal grating coupler.